The invention relates to color image sensor arrays, and more particularly to a multiplexing arrangement for controlling the data produced by the color image sensor array.
Monochrome image sensor arrays typically comprise a linear array of photodiodes which raster scan an image bearing document and convert the microscopic image area viewed by each photodiode to image signal charges. Following an integration period, the image signals are amplified and transferred to a common output line or bus through successively actuating multiplexing transistors.
To implement a full color array for the above application requires the use of more elaborate sensor arrays. Typically two implementations have been used. One implementation is to use the original monochrome sensor array as described above and place color filters, for instance red, green, blue for full color, on the photodiodes in an alternating manner. Every third photodiode would represent a color separation needing three such separations for one full color pixel. Even though full color images are produced, the resolution of the scan has been decreased by one third and further, each resulting pixel contains information for only one color instead of all three colors as is desirable. A second implementation involves the use of three linear arrays, each array having a color filter, and positioning the three arrays in parallel, one disposed above the other. The resolution is preserved but as the sensor arrays scan the page, memory would be required to delay the color information from two of the arrays to provide full color information for any one pixel. Memory requirements of this magnitude can be expensive to implement and also consume valuable space.
U.S. Pat. No. 4,972,255 to Suzuki et al. discloses a color sensor array containing three rows of photodiodes, each representing a different color. The array is used to gather full color information for an individual scanline without the use of memory. The controls and amplification for each line sensor are replicated three times. U.S. Pat. No. 4,278,995 to Fernside et al. discloses a sensor array containing three rows of photodiodes. The use of delay lines enables full color information for an individual scanline. U.S. Pat. No. 4,737,854 to Tandon et al. discloses an image sensor array having two stage transfer. U.S. Pat. No. 4,761,683 to Matteson et al. discloses a charge transfer system for multiple sensor row arrays using storage. U.S. Pat. No. 4,668,333 to Tandon et al., U.S. Pat. No. 4,690,391 to Stoffel et al., U.S. Pat. No. 4,695,716 to Tandon et al., and U.S. Pat. No. 4,735,671 to Stoffel et al. disclose methods and apparatuses for fabricating full width arrays from single sensor chips. U.S. Pat. No. 4,556,800 to Ohta et al. discloses an optical image sensing apparatus which has grouped photosensors connected in common and also discloses a grouped data transfer method. U.S. Pat. No. 4,745,482 to Baumeister discloses an electronic recorder including and image sensor having a linear array of photosites and a parallel method to read information out of the photosites. U.S. Pat. No. 4,322,752 to Bixby discloses a fast frame readout sensor which formats the sensor into blocks of photosite rows for the purpose of readout. U.S. Pat. No. 4,891,690 to Hasegawa et al. discloses a color sensor apparatus using three image sensors with associated electronics and memory to buffer the red, green and blue information from the sensors. JP-A1-2-153678 (Kyohgoku) discloses a full color sensor system having three linear arrays wherein a common amplifier is used for the three arrays.